text: """
  Copyright 2013 Steven Diamond
  
  This file is part of CVXPY.
  
  CVXPY is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  
  CVXPY is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  
  You should have received a copy of the GNU General Public License
  along with CVXPY.  If not, see <http://www.gnu.org/licenses/>.
  """
  
  from cvxpy.expressions.expression import Expression
  from cvxpy.atoms.affine.reshape import reshape
  
  
  def vec(X):
      """Flattens the matrix X into a vector in column-major order.
  
      Parameters
      ----------
      X : Expression or numeric constant
          The matrix to flatten.
  
      Returns
      -------
      Expression
          An Expression representing the flattened matrix.
      """
      X = Expression.cast_to_const(X)
      return reshape(X, (X.size,))
  